Posted by John B [172.69.46.31] on Friday, March 01, 2019 at 13:15:32 :
In Reply to: Re: Man...Busy Day! posted by Kevin in Ohio [172.68.65.219] on Thursday, February 28, 2019 at 12:54:14 :
Having spent 22 years with the tools, and 28 years as an inspector in the electrical trade, in Ontario Canada I have seen this type of installation many many times. There has always been confusion with what is grounding and what is bonding. To keep it simple, ie. a house with a 100 or 200 amp service, the 120/240 power comes into the house to the common type "service entrance panel". This panel is certified, and identified as such, has a main breaker, a brass screw or copper strap connecting the neutral bar to the back of the metal enclosure, and a barrier plate to cover that unfused portion of the panel.
The ground conductor from the rods, plate, whatever, terminates to the neutral bar in the service entrance section of the panel, and after that everything else is bonding. The bare conductors in the cables extend from the panel enclosure and should connect to every electrical box, and device that has a bonding screw. Some extras also to be bonded are internal metal water and gas pipes etc., depending on your local regulations. Therefore these bonding conductors are simply bonding everything back to the panel enclosure, and in turn back to the neutral bar and grounding electrode by means of that all important bonding screw or strap in the service entrance section of the panel.
The power supply to the garage can of course be overhead, or an underground raceway or cable.
If using an overhead 3 wire triplex to the garage a service entrance type panel with appropriate grounding is required as you are not carrying bonding with you. You treat it as being a new and separate service.
If you are using an underground 3 wire cable having its own bonding conductor, then you can use a regular sub panel as it has no neutral to panel enclosure ( case - box ) provision, ie. the brass screw or strap. However if the panel is a service entrance panel, then remove the brass screw or strap to separate the neutral from the enclosure as the bonding is coming from the house panel. Otherwise with the screw or strap in place the white neutral conductor and bare conductor of the cable are paralleling each other. There are thousands and thousands that have not been removed, but the system works just the same.
If you are using an underground raceway, you can do it either way, with the 3 power conductors or pull the bonding conductor as well. If you don't pull the bonding conductor then treat it as a new service with the service entrance panel and grounding.
This method of course meets the Canadian Code, There may be some variation to other countries including the USA. Years ago I have heard of neutral and bond conductors all being terminated to the same bar or even the panel enclosure. And maybe even no barrier plate in the service entrance panel. I trust that this info may clear up some questions re grounding and bonding as they are two different things.
PS. Incidentally regarding inspectors. About 15 to 20 years ago a main power upgrade was done at a local federal prison. The cost of the job was just a few thousand short of two million dollars. It was an out of town contractor that was awarded the job. After meeting the foreman, getting familiar with the site, the scope of their work, he told me he was always relieved when meeting the inspector for the first time to see the grey or white hair. JJB.